1. Field of the Invention
The present invention relates to a front vehicle body structure, and more particularly, to a front vehicle body structure in which a radiator panel lower extending in a width direction of a vehicle is mounted between front ends of right and left side frames extending in a longitudinal direction of the vehicle body, and a bumper extending in the width direction of the vehicle is mounted at the front ends of the right and left side frames via a shock absorbing member.
2. Description of Related Art
A strength and rigidity of a vehicle body is required to minimize a deformation of a vehicle compartment, which is a living space of a passenger, so that safety of the passenger for a crash of the vehicle is secured. In the case of a front collision, a front part of the vehicle is deformed as a crash zone so as to absorb a shock load, whereby a shock caused to the vehicle compartment, which is located at the rear of the front part, is reduced to decrease an injury criterion to which the passenger is exposed.
There has been known the following structure as the vehicle front body structure of this type. Specifically, the structure includes a radiator panel lower between front ends of right and left side frames, and shock absorbing members that are provided at the front ends of the right and left side frames, and that are subjected to an axial compression plastic deformation due to a shock load in an amount not less than a predetermined value input to the front ends of the right and left side frames. Further, a bumper is provided between the front ends of the right and left shock absorbing members.
For example, Japanese Patent Application Laid-Open (JP-A) No. 2006-76455 describes a structure whose side view is illustrated in FIG. 5. Specifically, a radiator panel lower 102 extending in the width direction of the vehicle is provided between front ends of right and left side frames 101 extending in the longitudinal direction of the vehicle, and crash boxes 103 serving as a shock absorbing member are coaxially provided to the front ends of the right and left side frames 101. The crash boxes 103 are subjected to an axial compression plastic deformation, when a shock load in an amount not less than a predetermined value is input to the front ends of the right and left side frames 101. A front bumper reinforce 104 extending in the width direction of the vehicle is mounted between the front ends of the right and left crash boxes 103.
Further, right and left second members 106 extending in the longitudinal direction are disposed below the right and left side frames 101. The rear ends of the second members 106 are coupled to front ends of sub-frames 105. The front ends of the second members 106 are coupled to each other by a bumper reinforce 107 disposed substantially parallel to the front bumper reinforce 104. The second members 106 are sandwiched between a lower end of a vertical column 109 of the radiator panel 108 and the radiator panel lower 102, and, with this state, they are coupled to the vertical column 109 and the radiator panel 102.
When the front vehicle part hits a side face of another vehicle, the bumper reinforce 107 is brought into contact with a side sill of the other vehicle. When the shock load is input to the second members 106 through the bumper reinforce 107, the second members 106 are deformed by an axial compression, thereby absorbing the shock load. On the other hand, when the shock load is input from a front bumper reinforce 104 to the side frame 101, the crash box 103 on the crash side is deformed by the axial compression, thereby absorbing the shock load.
(JP-A No. 2008-195094 describes another structure, whose perspective view is illustrated in FIG. 6. A frame-like sub-frame 115 is disposed below right and left side frames 111 extending in the longitudinal direction of the vehicle body, the frame-like sub-frame 115 including a pair of right and left vertical members 116 extending in the longitudinal direction of the vehicle body, and a front lateral member 117 and a rear lateral member 118 that extend in the width direction of the vehicle for linking front and rear ends of the vertical members 116. Both right and left front ends of the sub-frame 115 are supported by a pair of right and left linking members 112 projecting downward from the bottom surfaces of the front ends of the side frames 111, while the right and left rear ends are supported by kick-up units that are bent downward at the rear of the side frames 111.
A pair of right and left lower radiator support brackets 119 for supporting the lower part of the radiator is provided, the lower radiator support brackets 119 projecting from the front lateral member 117 of the sub-frame 115 toward the front of the vehicle body. A radiator upper stay 121 that supports an upper part of the radiator is provided between upper ends of radiator side stays 120 projecting from the front ends of the side frames 111.
With this structure, when a front collision occurs, the shock load input to the lower radiator support brackets 119 is directly transmitted to the sub-frame 115 from the front lateral member 117, whereby the shock absorbing efficiency of the sub-frame 115 can be enhanced, and a large-sized radiator can be mounted.
According to JP-A No. 2006-76455, when the front part of the vehicle body hits a side face of another vehicle, the bumper reinforce 107 is brought into contact with a side sill of the other vehicle. When the shock load is input to the second members 106 through the bumper reinforce 107, the second members 106 are deformed by an axial compression, thereby absorbing the shock load. On the other hand, when the shock load is input from the front bumper reinforce 104 to the side frame 101, the crash box 103 on the crash side is deformed by the axial compression, thereby absorbing the shock load.
In the case of full-overlap front collision in which a whole front part of a vehicle body collides against a concrete barrier or the like at a substantially right angle, the shock load is transmitted so as to be distributed to the right and left crash boxes 103 through the front bumper reinforce 104 and to the right and left second members 106 through the bumper reinforce 107, whereby the shock load is absorbed by the axial compression deformation of the right and left crash boxes 103 and the right and left second members 106.
On the other hand, in the case of an offset front collision in which a part of the front part of the vehicle body collides against the concrete barrier or the like, the shock load is transmitted to one of the crash boxes 103 through the front bumper reinforce 104 and to one of the second members 106 through the bumper reinforce 107. Therefore, shock load that is larger than the one expected in the case of the full-overlap collision is transmitted to the crash box 103 and the second member 106. Accordingly, the axial compression deformation that is larger than the one in the case of the full-overlap front collision is caused in the crash box 103 and the second member 106.
Consequently, in order to optimize the rigidity and strength of the crash boxes 103 and the second members 106 with the offset front collision being defined as a reference, the rigidity and strength of the right and left crash boxes 103 and the second members 106 have to be set significantly higher. When an offset front collision occurs in a vehicle provided with the crash boxes 103 and the second members 106, which are set with the offset front collision being defined as a reference, the shock load can be efficiently absorbed by the axial compression deformation of only one of the crash boxes 103 and one of the second members 106.
On the other hand, when the full-overlap front collision occurs in the vehicle provided with the crash boxes 103 and the second members 106 having the rigidity and strength set with the offset front collision being defined as a reference, the shock load is transmitted so as to be distributed to the right and left crash boxes 103 and the right and left second members 106. The crash boxes 103 and the second members 106, having the rigidity and strength set high, are deformed in a small amount, resulting in that the shock load cannot sufficiently be absorbed, and the remaining shock load might increase.
Similarly, in JP-A No. 2008-195094, in the case of the full-overlap front collision, the shock load is transmitted to the sub-frame 115 so as to be distributed to the right and left lower radiator support brackets 119 from the front lateral member 117, whereby the shock load is absorbed.
On the other hand, in the case of the offset front collision, the shock load is transmitted to the sub-frame 115 from one of the lower radiator support brackets 119 through the front lateral member 117, so that the shock load larger than the one expected in the case of the full-overlap front collision is transmitted to the sub-frame 115 from one of the lower radiator support brackets 119. Therefore, deformation larger than the one in the case of the full-overlap front collision is generated.
Accordingly, in order to optimize the rigidity and strength with the offset front collision being defined as a reference, the rigidity and strength of the sub-frame 115 and the other members have to be set significantly higher. When an offset front collision occurs in a vehicle provided with the members, which are set with the offset front collision being defined as a reference, the shock load can efficiently be absorbed by the deformation of the sub-frame 115.
On the other hand, when the full-overlap front collision occurs in the vehicle provided with the members set with the offset front collision being defined as a reference, the shock load is transmitted to the sub-frame 115 through the front lateral member 117 so as to be distributed to the right and left lower radiator support brackets 119. The sub-frame 115, having the rigidity and strength set high with the offset front collision being defined as a reference, is deformed in a small amount, resulting in that the shock load cannot sufficiently be absorbed, and the remaining shock load might increase.